1. Field of the Invention
The present invention relates to an optical system, an imaging apparatus, and a method for forming an image by the optical system.
2. Related Background Art
An optical system having a lens made of a glass medium with a high refractive index has been known. As for such an optical system, there has been proposed a one having a two-lens-group configuration composed of, in order from an object, a negative lens group and a positive lens group such as Japanese Patent Application Laid-Open No. 2005-134887.
Although the conventional optical system has a lens made of a glass medium with a high refractive index, there still has a problem that spherical aberration and curvature of field cannot be sufficiently corrected.